III-V lateral bipolar junction transistor on local facetted buried oxide layer

ABSTRACT

A bipolar junction transistor (LBJT) device that includes a base region of a first III-V semiconductor material having A first band gap; and emitter and collector regions present on opposing sides of the base region, wherein the emitter and collector regions are comprised of a second III-V semiconductor material having a wider band gap than the first III-V semiconductor material. A dielectric region is present underlying the base region, emitter region and the collect region. The dielectric region has an inverted apex geometry. The sidewalls of dielectric region that extend to the apex of the inverted apex geometry are present on facets of a supporting substrate III-V semiconductor material having a {110} crystalline orientation.

BACKGROUND Technical Field

The present disclosure relates to a bipolar junction transistor (BJT)structure, and more particularly to lateral bipolar junctiontransistors.

Description of the Related Art

Heterojunction bipolar junction transistors (HBTs) known in the artinclude a heterojunction, i.e., a junction of two semiconductormaterials having different band gaps, that coincide with a p-n junctionbetween the base and the emitter. The heterojunction at which twodifferent semiconductor materials having different band gaps are joinedcoincide with the p-n junction. The wider band gap of the emitterrelative to the band gap of the base in an HBT increases the currentgain relative to a bipolar junction transistor employing a samesemiconductor material across the base and the emitter and havingsimilar physical dimensions and doping profiles for the base andemitter.

SUMMARY

In one aspect, the present disclosure provides a lateral bipolarjunction transistors (LBJT) device. The bipolar junction transistor mayinclude a base region of a first III-V semiconductor material having thefirst band gap; and emitter and collector regions present on opposingsides of the base region. The emitter and collector regions are composedof a second III-V semiconductor material having a wider band gap thanthe first III-V semiconductor material. A dielectric region is presentunderlying the base region, emitter region and the collect region. Thedielectric region has an inverted apex geometry. The sidewalls of thedielectric region extending to the apex of the inverted apex geometryare present on facets of a supporting substrate III-V semiconductormaterial having a {110} crystalline orientation.

In another embodiment, the bipolar junction transistor includes asubstrate of a III-V semiconductor material having a trench with aninverted apex geometry. The sidewalls of the trench that lead to theinverted apex are provided by facets of the supporting substrate III-Vsemiconductor material having a {110} crystalline orientation. Adielectric fill is present within the trench having the inverted apexgeometry. The dielectric fill having a planar surface opposite a base ofthe dielectric fill that is in contact with the inverted apex of thetrench. The base region of the bipolar junction transistor is presentbetween an emitter region and a base region of the bipolar junctiontransistor. The emitter region, base region and the collector region ofthe bipolar junction transistor are present on the planar surface of thedielectric fill.

In another aspect, a method of forming a bipolar junction transistor isprovided that includes forming a III-V semiconductor material for a baseregion atop a III-V semiconductor substrate; and forming emitter andcollector regions on opposing sides of the base region. In a followingstep, the III-V semiconductor substrate is etched selectively to facetshaving a {110} crystalline orientation. The etch process provides atrench having the inverted apex geometry underlying at least the baseregion.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a side cross-sectional view of a lateral bipolar junctiontransistor (LBJT) device that includes a dielectric region that ispresent underlying the base region, the emitter region and the collectregion of the device, wherein the dielectric region has an inverted apexgeometry, in which the sidewalls of the dielectric region that extend tothe apex of the inverted apex geometry are present on facets of asupporting substrate III-V semiconductor material having a {110}crystalline orientation, in accordance with one embodiment of thepresent disclosure.

FIG. 2 is a side cross-sectional view of an initial structure forforming a lateral bipolar junction transistor (LBJT) as depicted in FIG.1, in which the initial structure includes a first III-V semiconductormaterial epitaxially formed on a substrate III-V semiconductor material,in accordance with one embodiment of the present disclosure.

FIG. 3 is a side cross-sectional view of sacrificial extrinsic basestructure formed on a base region portion of the first III-Vsemiconductor material, in accordance with one embodiment of the presentdisclosure.

FIG. 4 is a side cross-sectional depicting removing exposed portions ofthe III-V semiconductor material for the base region selectively to theIII-V semiconductor substrate, and epitaxially growing a III-Vsemiconductor material having a wider band gap than the III-Vsemiconductor material for the base region to provide the emitter andcollector regions on opposing sides of the base region, in accordancewith one embodiment of the present disclosure.

FIG. 5 is a side cross-sectional view depicting forming a spacer onsidewalls of the sacrificial extrinsic base structure, and forming aninterlevel dielectric layer having an upper surface coplanar with theupper surface of the interlevel dielectric layer, in accordance with oneembodiment of the present disclosure.

FIG. 6 is side cross-sectional view depicting removing the sacrificialextrinsic base structure.

FIG. 7 is a side cross-sectional view depicting etching the III-Vsemiconductor substrate selectively to facets having a {110} crystallineorientation, in which the etch process provides a trench having theinverted apex geometry underlying at least the base region, inaccordance with one embodiment of the present disclosure.

FIG. 8 is a side cross-sectional view depicting filling the trenchhaving the inverted apex geometry with a dielectric material.

FIG. 9 is a side cross-sectional view depicting forming an extrinsicbase region atop the base region of the bipolar junction transistor thatis depicted in FIG. 8.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments is intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “positioned on”means that a first element, such as a first structure, is present on asecond element, such as a second structure, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element. The term“direct contact” means that a first element, such as a first structure,and a second element, such as a second structure, are connected withoutany intermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

The term “bipolar junction transistor (BJT)” denotes is a semiconductordevice formed by two P-N junctions whose function is amplification of anelectric current. Bipolar transistors are made from 3 sections ofsemiconductor material, i.e., alternating P-type and N-type conductivitysemiconductor materials, with two resulting P-N junctions. As will bedescribed in greater detail below the (BJT) devices disclosed herein arelateral bipolar junction transistors (LBJT). The term “lateral” as usedto describe a BJT device denotes that means that the dimension extendingfrom the beginning of the emitter through the base to the collector ishorizontally orientated or is parallel with the upper surface of thesubstrate in which the emitter/base/collector, i.e., NPN or PNPjunction, is formed. The LBJT devices disclosed herein are composed oftype III-V semiconductor materials. The term “III-V semiconductor”denotes a semiconductor material that includes at least one element fromGroup III of the Periodic Table of Elements and at least one elementfrom Group V of the Periodic Table of Elements. Typically, the III-Vcompound semiconductors are binary, ternary or quaternary alloysincluding III/V elements. In contrast to type III-V semiconductormaterials, by “type IV semiconductor” it is meant that the semiconductormaterial includes at least one element from Group IVA (i.e., Group 14)of the Periodic Table of Elements.

The present disclosure provides lateral bipolar junction transistors(LBJT), and methods of forming LBJT devices including III-Vsemiconductor materials. III-V semiconductor materials are greatcandidates for lateral bipolar junction transistors and can offer highcut off frequency for both NPN and PNP types. Additionally, in someapplications a high voltage LBJT device is preferred for high voltageapplications. In some scenarios, the LBJT device is to be disconnectedfrom the underlying supporting semiconductor substrate, leading to theLBJT being formed on a semiconductor on insulator (SOI) substrate. TypeIII-V semiconductor on insulator substrates are not readily availablefor commercial production.

The methods and structures provided by the present disclosure formlateral bipolar junction transistors on III-V semiconductor materials,e.g., type III-V semiconductor substrates, followed by selectivelyetching the type III-V semiconductor material under the base region ofthe lateral bipolar junction transistor. The etch process may alsoextend laterally under the emitter and collector regions of the lateralbipolar junction transistor. In some embodiments, some over-etch may bedesirable to disconnect the emitter/collector from the substrate. Thecavity that is formed by the aforementioned etch process may be filledwith an isolating material, e.g., a dielectric material, such as anoxide, creating a buried oxide isolation region. This process provides aIII-V lateral bipolar junction transistor on any kind of III-Vsupporting structure. The methods and structures of the presentdisclosure are now described with greater detail with reference to FIGS.1-9.

FIG. 1 depicts one embodiment of an LBJT device that includes a baseregion 15 of a first III-V semiconductor material having the first bandgap; and emitter regions 20 and collector regions 25 present on opposingsides of the base region 15. The emitter region 20 and collector region25 are comprised of a second III-V semiconductor material having a widerband gap than the first III-V semiconductor material that provides thebase region 15. The term “band gap” refers to the energy differencebetween the top of the valence band (i.e., EV) and the bottom of theconduction band (i.e., EC).

For example, in some embodiments, the first III-V semiconductor materialthat provides the base region 15 is composed of indium gallium arsenide(InGaAs). In some examples, indium gallium arsenide (InGaAs) has a bandgap of about 0.8 eV. In one example, to provide that the emitter region20 and the collector region 25 have a wider band gap than the baseregion 15, the emitter region 20 and the collector region 25 may beprovided by a type III-V semiconductor material, in which aluminum (Al)is incorporated to increase the band gap of the material. For example,each of the emitter region 20 and the collector region 25 may becomposed of indium gallium aluminum arsenide (InGa(Al)As). As will bedescribed in further detail below, each of the emitter region 20, thebase region 15 and the collector region 25 may be formed using anepitaxial deposition process.

The base region 15 is the region where an input current triggers alarger current from the emitter region 20 to the collector region 25 ofthe transistor. The role of the base region 15 is to function as anamplifier which causes the emitter-to-collector current to besignificantly larger than the base current. When the base currentreceives an input current, a larger current then flows from the emitterregion 20 to the collector region 25.

The base region 15 of the transistor has an opposite polarity, i.e.,conductivity type, from the emitter region 20 and the collector region25. The term “conductivity type” means that a region is either doped toan n-type conductivity or a p-type conductivity. For example, when thebase region 15 is doped to an n-type conductivity, the emitter region 20and the collector region 25 is doped to a p-type conductivity, and thetransistor is referred to as a PNP transistor. In another example, whenthe base region 15 is doped to a p-type conductivity, the emitter region20 and the collector region 25 is doped to an n-type conductivity, andthe transistor is referred to as an NPN transistor. In an NPN bipolartransistor, the collector current is due to electrons flowing from theemitter region 20 to the collector region 25. In an PNP bipolartransistor, the collector current is due to holes flowing from theemitter region 20 to the collector region 25.

In some embodiments, the base region 15 is composed of an epitaxiallyformed in situ doped III-V semiconductor material that may be singlecrystal or polycrystalline. The base region 15 is typically doped to ann-type or p-type conductivity using a dopant concentration that is lessthan the dopant concentration in the overlying extrinsic base region 30.For example, the dopant that dictates the conductivity type of the baseregion 15 may be present in the III-V semiconductor material thatprovides the base region 15 in a concentration ranging from 10¹⁶atoms/cm³ to 10¹⁹ atoms/cm³.

Still referring to FIG. 1, the emitter region 20 and the collectorregion 25 may be present on opposing sides of the base region 15. Theemitter region 20, and the collector region 25 may be composed ofepitaxially formed in situ doped III-V semiconductor material. The insitu doped III-V semiconductor material for the emitter region andcollector region 20, 25 may be single crystal or polycrystalline.

In some embodiments, the epitaxially formed in situ doped III-Vsemiconductor material that provides the emitter region 20, and thecollector region 25 may be composed of a material having a band gapsubstantially equal to the band gap of the band gap of the base region15. For example, the in situ doped III-V semiconductor material thatprovides the emitter region 15, and the collector region 20 may becomposed of the same III-V semiconductor material of the base region 10.In other embodiments, the epitaxially formed in situ doped III-Vsemiconductor material that provides the emitter region 20, and thecollector region 25 may be composed of a material having a band gap thatis greater than the band gap of the III-V semiconductor material of thebase region 15.

The emitter region 20 and the collector region 25 are typically doped toa conductivity type that is opposite the conductivity type of the baseregion 15. For example, if the base region 15 is doped to an n-typeconductivity, the emitter region 20 and the collector region 25 aredoped to a p-type conductivity. For example, if the base region 15 isdoped to a p-type conductivity, the emitter region 20 and the collectorregion 25 are doped to an n-type conductivity. The dopant that dictatesthe conductivity type of the emitter region 20 and the collector region25 may be present in the III-V semiconductor material that provides theemitter region 20 and collector region 25 in a concentration rangingfrom 10¹⁸ atoms/cm³ to 10²¹ atoms/cm³. In some embodiments, the devicedesign may include that the emitter region 20 and collector region 25are doped more heavily than the base region 15.

In some embodiments, a dielectric region 10 is present underlying thebase region 15, emitter region 20 and the collect region 25. In someembodiments, the dielectric region 10 has an inverted apex geometry,wherein sidewalls of dielectric region extending to the apex A1 of theinverted apex geometry are present on facets P1, P2 of a supportingsubstrate III-V semiconductor material 5. In some embodiments, thefacets P1, P2 of the supporting substrate III-V semiconductor materialhave a {110} crystalline orientation.

In some embodiments, each facet P1, P2 provides a substantially linearsidewall for a notch (also referred to as a trench with an inverted apexgeometry) that is angled at approximately 45° relative to an uppersurface of the plane in the direction extending from the upper surfaceof the emitter region 20 extending across the base region 15 to thecollector region 25. Each facet P1, P2 may extend from a sidewall of anisolation trench 6 formed in the supporting substrate III-Vsemiconductor material 5. As depicted in FIG. 1, the two facets P1, P2intersect at an apex A1 providing the base of the dielectric region 10.Because the apex A1 is pointed downward, i.e., in a direction away fromthe overlying emitter region 20, base region 15 and collector region 25,the apex A1 may be referred to as inverted. For example, an invertedapex A1 is the geometry of the base of the dielectric region 10. Forexample, the dielectric region 10 may be provided by a dielectric fillpresent within the trench that is formed in the supporting substrateIII-V semiconductor material 5 having the inverted apex geometry. Thedielectric region 10, i.e., dielectric fill, having a planar surfaceopposite a base of the dielectric fill that is in contact with theinverted apex of the trench. The planar surface is the surface of thedielectric region 10 that is contacting the emitter region 20, baseregion 15 and the collector region 25.

The dielectric region 10 may be provided by any dielectric material thatcan be formed using a flowable dielectric process. For example, thedielectric region 10 may be composed of organosilicate glass (OSG),fluorine doped silicon dioxide, carbon doped silicon dioxide, poroussilicon dioxide, porous carbon doped silicon dioxide, spin-on organicpolymeric dielectrics (e.g., SILK™), hydrogen silsesquioxane (HSQ),methylsilsesquioxane (MSQ), and combinations thereof.

The supporting substrate III-V semiconductor material 5 can be providedby an indium containing III-V semiconductor material. For example, thesupporting substrate III-V semiconductor substrate 5 may be composed ofindium phosphide (InP). It is noted that other III-V semiconductormaterials can provide the supporting substrate III-V semiconductormaterial 5 so long as the material may be etched to provide the facetsP1, P2 leading to the inverted apex A1 structure depicted in FIG. 1. Forexample, the III-V semiconductor material may provide the materialselected be etched with a hydrochloric etch that is selective to facetsof the material for the supporting substrate III-V semiconductormaterial having a {110} crystalline orientation. Examples of other typeIII-V semiconductor materials besides indium phosphide (InP) that may besuitable for the supporting substrate III-V semiconductor material mayinclude indium antimonide (InSb), indium arsenic (InAs), indium nitride(InN), indium gallium phosphide (InGaP), indium gallium nitride (InGaN),indium arsenide antimonide (InAsSb), indium gallium antimonide (InGaSb),aluminum gallium indium phosphide (AlGaInP), indium gallium arsenidephosphide (InGaAsP), indium arsenide antimonide phosphide (InArSbP),aluminum indium arsenide phosphide (AlInAsP), indium gallium arsenidenitride (InGaAsN), indium aluminum arsenide nitride (InAlAsN), galliumindium nitride arsenide aluminum antimonide (GaInNAsSb), gallium indiumarsenide antimonide phosphide (GaInAsSbP), and combinations thereof(including combinations with indium phosphide).

In some embodiments, the dielectric region 10 is an air gap. In theembodiments, in which the dielectric region 10 is an air gap, theemitter region 20, base region 15 and the collector region 10 aresuspended over a trench, i.e., air gap, having a base provided by theinverted apex geometry described above resulting from the facets P1, P2,i.e., angled facets of approximately 45°, intersecting at the downwardpointing apex A1.

Still referring to FIG. 1, the isolation regions 6 may be trenchisolation regions having a depth that extends through the emitter region20 and collector region 25 into the supporting substrate III-Vsemiconductor material 5. The isolation regions 6 may be composed of anydielectric material, such as an oxide, nitride or oxynitride material.For example, the isolation region 6 may be composed of silicon oxide(SiO₂). The isolation regions 6 positioned on opposing sides of thefunctional features of the lateral bipolar junction transistor providefor device isolation.

Referring to FIG. 1, the lateral bipolar junction transistor of claim 1further comprising an extrinsic base region 30 comprised of a dopedpolycrystalline III-V semiconductor material or a doped singlecrystalline III-V semiconductor material that is present atop the baseregion. Examples of III-V semiconductor materials suitable for theextrinsic base region 30 include indium aluminum arsenic (InAlAs),indium gallium arsenide (InGaAs), gallium arsenide (GaAs), galliumphosphide (GaP), indium antimonide (InSb), indium arsenic (InAs), indiumnitride (InN), indium phosphide (InP), aluminum gallium arsenide(AlGaAs), indium gallium phosphide (InGaP), aluminum indium arsenic(AlInAs), aluminum indium antimonide (AlInSb), gallium arsenide nitride(GaAsN), and combinations thereof. The extrinsic base region 30 istypically doped to a same conductivity type as the base region 15. Forexample, if the base region 15 is doped to an n-type conductivity, theextrinsic base region 30 is also doped to an n-type conductivity. Thedopant concentration of the extrinsic base region 30 is typicallygreater than the dopant concentration of the base region 15. Forexample, the dopant concentration of the n-type or p-type dopant in theextrinsic base region 30 may range from 10¹⁸ atoms/cm³ to 10²¹atoms/cm³. The extrinsic base region 30 is present within the width ofthe base region 10. Spacers 31 of a dielectric material, such as anoxide, nitride or oxynitride material, are present on the sidewalls ofthe extrinsic base region 30.

In some embodiments, the LBJT device that is depicted in FIG. 1 may besuitable for high speed applications. FIGS. 2-9 depict one embodiment ofa method for forming the LBJT devices depicted in FIG. 1.

FIG. 2 depicts one embodiment of an initial structure for forming alateral bipolar junction transistor (LBJT) as depicted in FIG. 1, inwhich the initial structure includes a first III-V semiconductormaterial, for the base region 15, that is epitaxially formed on asubstrate III-V semiconductor material that provides the supportingsubstrate III-V semiconductor material 5. The supporting substrate III-Vsemiconductor material 5 may be indium phosphide (InP). The supportingsubstrate III-V semiconductor material 5 may be an indium phosphide(InP) substrate; may be an indium phosphide (InP) layer that is arelaxed layer structure present atop a layer of a type IV semiconductor,such as silicon; or the indium phosphide (InP) that provides thesupporting substrate III-V semiconductor material 5 may be presentwithin a trench, e.g., wide aspect ratio trench. Further details for thesupporting substrate III-V semiconductor material 5 is provided in thedescription of the supporting substrate III-V semiconductor material 5provided above with reference to FIG. 1.

FIG. 2 further depicts epitaxially forming a first III-V semiconductormaterial, for the base region 15, on the upper surface of the supportingsubstrate III-V semiconductor material 5. “Epitaxial growth and/orepitaxial deposition” means the growth of a semiconductor material on adeposition surface of a semiconductor material, in which thesemiconductor material being grown has substantially the samecrystalline characteristics as the semiconductor material of thedeposition surface. The term “epitaxial material” denotes asemiconductor material that has substantially the same crystallinecharacteristics as the semiconductor material that it has been formedon, i.e., epitaxially formed on. In some embodiments, when the chemicalreactants are controlled, and the system parameters set correctly, thedepositing atoms of an epitaxial deposition process arrive at thedeposition surface with sufficient energy to move around on the surfaceand orient themselves to the crystal arrangement of the atoms of thedeposition surface. An epitaxial material has substantially the samecrystalline characteristics as the semiconductor material of thedeposition surface. For example, an epitaxial film deposited on a {100}crystal surface will take on a {100} orientation. The epitaxialdeposition process may be carried out in the deposition chamber of achemical vapor deposition (CVD) apparatus.

A number of different sources may be used for the deposition ofepitaxial type III-V semiconductor material for the III-V semiconductormaterial layer for the base region 15. In some embodiments, the sourcesfor epitaxial growth of type III-V semiconductor material include liquidor solid sources containing In, Al, As, Ga, N, P elements andcombinations thereof and/or a gas precursor selected from the groupconsisting of Trimethylaluminum (CH₃)₃Al, Trimethylgallium (CH₃)₃Ga,(TMG), Trimethylindium (TMI) (CH₃)₃IN, tertiary-butylphosphine (TBP),tertiary-butylarsine (TBA), phosphine (PH₃), arsine (AsH3) ammonia(NH3), and combinations thereof. The temperature for epitaxialdeposition of type III-V semiconductor materials typically ranges from350° C. to 700° C.

In one embodiment, the first III-V semiconductor material for the baseregion 15 is indium gallium arsenide (InGaAs). It is noted that othermaterials may be employed for the first III-V semiconductor material forthe base region 15 so long as material of the supporting substrate III-Vsemiconductor material 5 may be removed selectively to the first III-Vsemiconductor material for the base region 15. Examples of other typeIII-V semiconductor materials that may be suitable for first III-Vsemiconductor material for the base region 15 may include aluminumantimonide (AlSb), aluminum arsenide (AlAs), aluminum nitride (AlN),aluminum phosphide (AlP), gallium arsenide (GaAs), gallium phosphide(GaP), aluminum gallium arsenide (AlGaAs), gallium arsenide nitride(GaAsN), gallium arsenide antimonide (GaAsSb), aluminum gallium nitride(AlGaN), aluminum gallium phosphide (AlGaP), aluminum gallium arsenidephosphide (AlGaAsP), aluminum gallium arsenide nitride (AlGaAsN),gallium arsenide antimonide nitride (GaAsSbN), and combinations thereof.

The III-V semiconductor material layer for the base region 15 is dopedto an n-type or p-type conductivity. The III-V semiconductor materiallayer for the base region 15 may be in situ doped. The term “in situ”denotes that the dopant that dictates the conductivity type of amaterial is introduced while the material is being formed, e.g., duringthe epitaxial growth process. The term “p-type” refers to the additionof impurities to an intrinsic semiconductor that creates deficiencies ofvalence electrons. As used herein, “n-type” refers to the addition ofimpurities that contributes free electrons to an intrinsicsemiconductor. To provide an n-type dopant to the III-V semiconductormaterial, the dopant may be an element from Group IV or VI of thePeriodic Table of Elements. To provide a p-type dopant to the III-Vsemiconductor material, the dopant may be an element from Group II or VIof the Periodic Table of Elements. In an III-V semiconductor, atoms fromgroup II act as acceptors, i.e., p-type, when occupying the site of agroup III atom, while atoms in group VI act as donors, i.e., n-type,when they replace atoms from group V. Dopant atoms from group IV, such asilicon (Si), have the property that they can act as acceptors or donordepending on whether they occupy the site of group III or group V atomsrespectively. Such impurities are known as amphoteric impurities. Insome examples, the dopants that dictate the n-type or p-typeconductivity may include silicon (Si), iron (Fe), germanium (Ge) andcombinations thereof.

Still referring to FIG. 2, in one embodiment, after forming the firstIII-V semiconductor material for the base region 15, isolation regions 6may be formed on opposing sides of the region on which the functionalfeatures of the lateral bipolar junction are to be formed. The isolationregions 6 may be trench isolation regions. The trench isolation regionis formed utilizing, for example, lithography, and etching to form atrench, and filling of the trench with a trench dielectric by adeposition process, such as chemical vapor deposition.

FIG. 3 depicts one embodiment of a sacrificial extrinsic base structure29 being formed on a base region portion of the first III-Vsemiconductor material. The term “sacrificial” denotes that theextrinsic base structure formed at this process step is removed prior tothe final device structure. A functional extrinsic base structure willbe substituted for sacrificial extrinsic base structure 29. In oneembodiment, the sacrificial material that provides the sacrificialextrinsic base structure 29 may be composed of any material that can beetched selectively to the at least one of the III-V semiconductormaterial that provides the base region 15. In one embodiment, thesacrificial extrinsic base structure 29 may be composed of asilicon-including material, such as polysilicon. In another embodiment,the sacrificial extrinsic base structure 29 may be composed of adielectric material, such as an oxide, nitride or oxynitride material,or amorphous carbon. The extrinsic base structure 29 may be formed usingdeposition (e.g., chemical vapor deposition or spinning of a flowabledielectric) photolithography and etch processes (e.g., reactive ionetching). In some embodiments, the sacrificial extrinsic base structure29 may be composed of a nitride, amorphous silicon, hydrogensilsesquioxane (HSQ), silicon oxide (SiO₂), hafnium oxide (HfO₂), or acombination thereof.

FIG. 4 depicts removing exposed portions of the III-V semiconductormaterial for the base region 15 selectively to the III-V semiconductorsubstrate 5, and epitaxially growing a III-V semiconductor materialhaving a wider band gap than the III-V semiconductor material for thebase region 15 to provide the emitter and collector regions 20, 25 onopposing sides of the base region 15.

FIG. 4 depicts etching the first III-V semiconductor material layer toprovide the base region 15 of the LBJT device. In some embodiments, theetch mask, e.g., photoresist mask, that is used in defining the geometryof the sacrificial extrinsic gate structure 29 can be used in the etchprocess for defining the base region 15. In other embodiments, aseparate etch mask may be formed to protect the portion of the firstIII-V semiconductor material layer that provides the base region 15, orthe sacrificial gate structure 29 is used as the etch mask to define thebase region 15.

The exposed portions of the first III-V semiconductor material layer maybe removed while the portions of the first III-V semiconductor materiallayer that provides the base region 15 is protected by the overlyingsacrificial extrinsic gate structure 29, and any overlying photoresistmasks that may be employed. The etch process for etching the first III-Vsemiconductor material layer may be selective to the supportingsubstrate III-V semiconductor material layer 5. As used herein, the term“selective” in reference to a material removal process denotes that therate of material removal for a first material is greater than the rateof removal for at least another material of the structure to which thematerial removal process is being applied. For example, in oneembodiment, a selective etch may include an etch chemistry that removesa first material selectively to a second material by a ratio of 10:1 orgreater. The etch process for removing the exposed portions of thelattice matched III-V semiconductor material layer 10 may be a wet etchor a dry etch.

FIG. 4 also depicts epitaxially forming the emitter and collectorregions 20, 25 on the exposed portions of the supporting substrate III-Vsemiconductor material that is exposed by the aforementioned etchprocess for defining the base region 15. The emitter and collectorregions 20, 25 may be composed of single crystalline or polycrystallinematerial. The emitter and collector regions 20, 25 may be composed of aIII-V semiconductor material having a band gap that is the same orgreater than the band gap of the base region 15. For example, aluminum(Al) may be incorporated into the second III-V semiconductor material ofthe emitter region 20 and the collector region 25 to increase the bandgap of the material. For example, each of the emitter region 20 and thecollector region 25 may be composed of indium gallium aluminum arsenide(InGa(Al)As). It is noted that indium gallium aluminum arsenide(InGa(Al)As) is only one example for the second III-V semiconductormaterial that provides the emitter region 20 and the collector region25. For example, the epitaxially formed in-situ doped III-Vsemiconductor material for the emitter region 20 and the collectorregion 25 may be composed of at least one of aluminum antimonide (AlSb),aluminum arsenide (AlAs), aluminum nitride (AlN), aluminum phosphide(AlP), gallium arsenide (GaAs), gallium phosphide (GaP), indiumantimonide (InSb), indium arsenic (InAs), indium nitride (InN), indiumphosphide (InP), aluminum gallium arsenide (AlGaAs), indium galliumphosphide (InGaP), aluminum indium arsenic (AlInAs), aluminum indiumantimonide (AlInSb), gallium arsenide nitride (GaAsN), gallium arsenideantimonide (GaAsSb), aluminum gallium nitride (AlGaN), aluminum galliumphosphide (AlGaP), indium gallium nitride (InGaN), indium arsenideantimonide (InAsSb), indium gallium antimonide (InGaSb), aluminumgallium indium phosphide (AlGaInP), aluminum gallium arsenide phosphide(AlGaAsP), indium gallium arsenide phosphide (InGaAsP), indium arsenideantimonide phosphide (InArSbP), aluminum indium arsenide phosphide(AlInAsP), aluminum gallium arsenide nitride (AlGaAsN), indium galliumarsenide nitride (InGaAsN), indium aluminum arsenide nitride (InAlAsN),gallium arsenide antimonide nitride (GaAsSbN), gallium indium nitridearsenide aluminum antimonide (GaInNAsSb), gallium indium arsenideantimonide phosphide (GaInAsSbP), and combinations thereof, so long asproviding a band gap that is equal to or greater than the base region15.

The epitaxial deposition and in-situ doping process for forming theepitaxially formed in-situ doped single crystal III-V semiconductormaterial that provides the emitter and collector regions 20, 25 has beendescribed above for forming the first III-V semiconductor material thatprovides the base region 15. Therefore, the above description forepitaxial grown and in-situ doping for the first III-V semiconductormaterial that provides the base region 15 is suitable for providing atleast one embodiment of forming the material layers for the emitter andcollector regions 20, 25. The emitter and collector regions 15, 20 aredoped with a conductivity type dopant that is opposite the conductivitytype of the base region 15. The dopant that produces the n-type orp-type conductivity may be selected from silicon, germanium and iron.The dopant concentration of the emitter and collector regions 20, 25 mayrange from 10¹⁸ atoms/cm³ to 10²¹ atoms/cm³.

FIG. 5 depicts forming a spacer 31 on sidewalls of the sacrificialextrinsic base structure 29, and forming an interlevel dielectric layer35 having an upper surface coplanar with the upper surface of thesacrificial extrinsic base structure 29. The spacer 31 is typicallycomposed of a dielectric material, such as an oxide, nitride, oroxynitride material. In one example, when the spacer 39 is composed of anitride, the spacer 31 may be composed of silicon nitride, and when thespacer 39 is composed of oxide, the spacer 31 may be composed of siliconoxide. In another example, the spacer 31 is comprised of silicon nitrideor silicon boron carbon nitride (SiBCN). The spacer 31 may be formedusing a deposition process, such as chemical vapor deposition (CVD), andan anisotropic etchback method. The spacer 31 may be present on thesidewalls of the sacrificial extrinsic base structure 29, and may have athickness ranging from 1 nm to 15 nm.

FIG. 5 also depicts depositing an interlevel dielectric layer 35. Theinterlevel dielectric layer 35 may be any dielectric material, such asan oxide, e.g., silicon oxide, nitride, e.g., silicon nitride, and/oroxynitride. The interlevel dielectric layer 35 may then be planarized,e.g., by chemical mechanical planarization (CMP), to provide an uppersurface that is coplanar with the upper surface of the sacrificialextrinsic base structure 29.

FIG. 6 depicts removing the sacrificial extrinsic base structure 29 toprovide an opening 14 to the base region 15 composed of the first III-Vsemiconductor material. The extrinsic base structure 29 may be removedusing a wet or dry etch process. In one embodiment, the extrinsic basestructure 29 may be removed by at least one of an anisotropic etchprocess, such as reactive ion etch (RIE), or an isotropic etch process,such as a wet chemical etch. In one example, the etch process forremoving the extrinsic base structure 29 can include an etch chemistrythat is selective to the at first III-V semiconductor material of thebase region 15. The etch process for removing the extrinsic basestructure 29 may also be selective to the spacer 31.

FIG. 7 depicts etching the III-V semiconductor substrate 5 selectivelyto facets P1, P2 having a {110} crystalline orientation, in which theetch process provides a trench having the inverted apex geometry (apexA1) underlying at least the base region 15. The etch employed at thisstate of the process flow has an etch chemistry that decreases etch rateat the (110) planes. The etchant is introduced through the opening 14provided by removing the sacrificial extrinsic base structure 29, andpenetrates to the supporting substrate III-V semiconductor material 5through opening produced by removing portions of the first III-Vsemiconductor layer that provide the extrinsic base region 15, whichextend into and out of the plane of cross-section depicted in FIG. 7.Therefore, in some embodiments, a first etch stage, which can beprovided by an anisotropic etch, such as reactive ion etching (RIE) canremove portions of the first III-V semiconductor material layer thatprovide the base region 15 a positioned along a plane that extends intoand out of the page on which the cross-section for FIG. 7 is depicted.This etch step exposes portions of the supporting substrate III-Vsemiconductor material 5. An etch mask may protect the base portion 14of the first III-V semiconductor material during this stage of theprocess flow.

Once the supporting substrate III-V semiconductor material 5 is exposed,a portion of the supporting substrate III-V semiconductor material 5 maybe removed selectively to the remaining portion of the first III-Vsemiconductor material that provides the base region. The etch processfor removing the portion of the supporting substrate III-V semiconductormaterial 5 is selective to facets of the material for the supportingsubstrate III-V semiconductor material 5 to provide an inverted apexregion, i.e., trench 9 having the inverted apex geometry, depicted inFIG. 7.

In some embodiments, the etch process for removing the supportingsubstrate III-V semiconductor material, e.g., indium phosphide (InP),selectively to the first III-V semiconductor material, e.g., indiumgallium arsenide (InGaAs), that provides the base region 15 is a wetchemical etch that includes hydrochloric (HCl) acid. The hydrochloric(HCl) acid etch may include 18.5% hydrochloric (HCl) acid. Thehydrochloric (HCl) acid etch composition is selective to {110} crystalplane of the supporting substrate III-V semiconductor material 5, e.g.,indium phosphide (InP). In some embodiments, the selective etch of thesupporting substrate III-V semiconductor material 5, e.g., indiumphosphide (InP), stops at an angle of approximately 45 degrees. Thiscorresponds to a plane belonging to the {110} family for the supportingsubstrate III-V semiconductor material 5, e.g., indium phosphide (InP).The etch process may start with removing the portion of the supportingsubstrate III-V semiconductor material 5, e.g., indium phosphide (InP),that is underlying the base region 15, and may continue by over-etchinginto removing the supporting substrate III-V semiconductor material 5,e.g., indium phosphide (InP), that is underlying the emitter region 20and the collector region 25. The etch process may stop upon contactingthe sidewalls of the isolation regions 6 due to etch selectivity. Theetch process may include the facets P1, P2 intersecting at the invertedapex A1 to provide the trench 9 having the inverted apex geometry.

The selective nature of the HCl etch to the indium containing supportingsemiconductor III-V material 5 provides an inverted apex regionunderlying the emitter region 20, base region 15 and collector region25. The inverted apex region may remain unfilled to provide an air gapunderlying the emitter region 20, base region 15 and collector region25. To provide this embodiment, a sealing dielectric may be deposited toclose the opening through which the etchant reached the supportingsubstrate III-V semiconductor material 5 to provide the trench 9 havingthe inverted apex geometry. Thereafter, a functional extrinsic basestructure 30 is formed in the opening 14 that is formed by removing thesacrificial extrinsic base structure 29, as described below withreference to FIG. 9. In other embodiments, the trench 9 having theinverted apex geometry is filled with a solid dielectric to provide adielectric region 10 having an inverted apex geometry, as described withreference to FIGS. 8 and 9.

FIG. 8 depicts filling the trench 9 having the inverted apex geometrywith a dielectric material 10 filling the inverted apex region. Thedielectric 10 may be a flowable dielectric material. The flowabledielectric material may be an oxide, such as silicon oxide. It is notedthat the composition for the flowable dielectric material is not limitedto only oxides, as other dielectric materials may also be suitable forthe flowable dielectric material. For example, the flowable dielectricmaterial may be composed of a low-k dielectric material. In someexamples, the low-k dielectric that provides the flowable dielectricmaterial may have a dielectric constant of 4.0 or less (measured at roomtemperature, e.g., 25° C., and 1 atm). For example, a low-k dielectricmaterial suitable for the flowable dielectric material may have adielectric constant ranging from about 1.0 to about 3.0. Examples oflow-k materials suitable for the flowable dielectric material 25 includeorganosilicate glass (OSG), fluorine doped silicon dioxide, carbon dopedsilicon dioxide, porous silicon dioxide, porous carbon doped silicondioxide, spin-on organic polymeric dielectrics (e.g., SILK™), spin-onsilicone based polymeric dielectric (e.g., hydrogen silsesquioxane (HSQ)and methylsilsesquioxane (MSQ), and combinations thereof.

The flowable dielectric material that provides the dielectric 10 forfilling the trench 9 having the inverted apex geometry may be formedusing spin on glass (SOG) deposition and flowable chemical vapordeposition (FCVD). Spin on glass (SOG) compositions typically includessilicon oxide (SiO₂) and optionally dopants (either boron orphosphorous) that is suspended in a solvent solution. The SOG is appliedthe deposition by spin-coating. Spin-coating is a process used to coatthe deposition surface with material which is originally in the liquidform, wherein the liquid is dispensed onto the deposition surface inpredetermined amount, and the wafer is rapidly rotated. F or example,the deposition surface, e.g., substrate, may be rotated, i.e., spun, tospeeds as great as 6,000 rpm. During spinning, liquid is uniformlydistributed on the surface by centrifugal forces. The deposited materialmay then be solidified by a low temperature bake, e.g., baking attemperatures less than 200° C. The deposited material may also be curedusing an ultraviolet light application.

The flowable dielectric material that provides the dielectric 10 forfilling the trench 9 having the inverted apex geometry may also bedeposited using flowable chemical vapor deposition (FCVD). The flowabledielectric material deposited by flowable chemical vapor deposition(FCVD) may be a substantially carbon free silicon oxide (SiO₂) material.Flowable chemical vapor deposition (FCVD) provides for a liquid-likefilm that flows freely into trench like geometries to provide a bottomup, void-free and seam-free fill. Flowable chemical vapor deposition canfill gaps having aspect ratios of up to 30:1. One example, of a flowablechemical vapor deposition process is available from Applied Materialsunder the tradename Eterna FCVD system.

FIG. 9 depicting forming an extrinsic base region 30, i.e., functionextrinsic base region, atop the base region 15 of the bipolar junctiontransistor that is depicted in FIG. 8. The material layer for anextrinsic base region 30 of the LBJT device may include dopedpolycrystalline or single crystalline III-V semiconductor materials. Insome embodiments, the material layer for the base region 30 may bedeposited directly on the exposed surface of the base region 15, and mayfill an entirety of the opening 14 that is formed by removing thesacrificial extrinsic base region 29. The material layer for theextrinsic base 30 can be formed using similar epitaxial depositionmethods as described above for forming the first III-V semiconductormaterial that provided the base region 15, as well as the epitaxialdeposition process that provided the emitter and collector regions 20,25. In some embodiments, the material layer for the extrinsic baseregion 30 does not need to be epitaxially formed, e.g., when thematerial layer for the extrinsic base region 30 is composed of apolycrystalline material. The extrinsic base region 30 may be depositedusing chemical vapor deposition in which the deposition conditions areconfigured to form a polycrystalline material.

The material layer for an extrinsic base region 30 of the LBJT device istypically doped to a same conductivity type as the first III-Vsemiconductor material layer that provides the base region 15. Thedopant concentration of the extrinsic base region 30 may range from 10¹⁸atoms/cm³ to 10²¹ atoms/cm³. The dopant may be implanted by ionimplantation, or introduced in situ by gas phase doping.

FIG. 1 depicts one embodiment of forming contacts 36 a, 36 b, 36 c tothe emitter region 20, base region 15 and collector region 25,respectively. Forming contacts 36 a, 36 b, 36 c may begin with forming avia opening in the interlevel dielectric layer 35, and filling the viaopening with an electrically conductive material. In some embodiments,the via opening may be formed using pattern and etch processing. Theelectrically conductive material may be a metal, such as tungsten,titanium, aluminum, copper or a combination thereof, which may bedeposited using a method, such as physical vapor deposition, e.g.,plating and/or sputtering.

The methods and structures that have been described above with referenceto FIGS. 1-9 may be employed in any electrical device includingintegrated circuit chips. The integrated circuit chips including thedisclosed structures and formed using the disclosed methods may beintegrated with other chips, discrete circuit elements, and/or othersignal processing devices as part of either (a) an intermediate product,such as a motherboard, or (b) an end product. The end product can be anyproduct that includes integrated circuit chips, including computerproducts or devices having a display, a keyboard or other input device,and a central processor.

Having described preferred embodiments of III-V lateral bipolar junctiontransistor on local facetted buried oxide layer (which are intended tobe illustrative and not limiting), it is noted that modifications andvariations can be made by persons skilled in the art in light of theabove teachings. It is therefore to be understood that changes may bemade in the particular embodiments disclosed which are within the scopeof the invention as outlined by the appended claims. Having thusdescribed aspects of the invention, with the details and particularityrequired by the patent laws, what is claimed and desired protected byLetters Patent is set forth in the appended claims.

What is claimed is:
 1. A semiconductor device comprising: a base regionof a first III-V semiconductor material having a first band gap; andemitter and collector regions present on opposing sides of the baseregion, wherein the emitter and collector regions are comprised of asecond III-V semiconductor material having a wider band gap than thefirst III-V semiconductor material; and an air gap region underlying thebase region, emitter region and the collector region, the air gap regionhaving an inverted apex geometry, wherein sidewalls of the air gapregion extending to an apex of the inverted apex geometry are present onfacets of a supporting substrate having a {110} crystalline orientation,the facets extend from an outermost edge of each of the emitter regionand the collector region, and the air gap region being a single voidthat is present underlying a portion of each of the base region, theemitter region and the collector region.
 2. The semiconductor device ofclaim 1, wherein the semiconductor device is a bipolar junctiontransistor.
 3. The semiconductor device claim 2, wherein the bipolarjunction transistor is a lateral bipolar junction transistor.
 4. Thesemiconductor device of claim 2, further comprising an extrinsic regioncomprised of a doped polycrystalline III-V semiconductor material or adoped single crystalline III-V semiconductor material that is presentatop the base region.
 5. The semiconductor device of claim 1, whereinthe supporting substrate is comprised of a III-V semiconductor material.6. The semiconductor device of claim 1, wherein a position of the facetsprovide that an upper surface of the air gap region is in direct contactwith a base surface for an entirety of each of said base region and saidemitter and collector regions.
 7. The semiconductor device of claim 1,wherein the supporting substrate semiconductor material is indiumphosphide (InP).
 8. The semiconductor device of claim 7, wherein thebase region is comprised of indium gallium arsenide (InGaAs).
 9. Thesemiconductor device of claim 1, wherein the emitter region and thecollector region are a type III-V semiconductor including aluminum toincrease the band gap of the second III-V semiconductor material to begreater than the first III-V semiconductor material.
 10. A semiconductordevice comprising: a substrate of a semiconductor material having atrench with an inverted apex geometry, wherein sidewalls of the trenchthat lead to the inverted apex are provided by facets of the substratesemiconductor material having a {110} crystalline orientation; an airgap fill present within the trench having the inverted apex geometry,the air gap fill having a planar surface opposite a base of the air gapfill that is in contact with an apex of the trench; and a base regionpresent between an emitter region and a collector region of a bipolarjunction transistor, wherein an entirety of a base surface for each ofthe emitter region, the base region and the collector region is presentdirectly on the planar surface of the air gap fill.
 11. Thesemiconductor device of claim 10, wherein the semiconductor device is abipolar junction transistor.
 12. The semiconductor device of claim 11,wherein the base region comprises a first III-V semiconductor materialhaving a first band gap; and the emitter and collector regions arecomprised of a second III-V semiconductor material having a wider bandgap than the first III-V semiconductor material.
 13. The semiconductordevice of claim 11, further comprising an extrinsic region comprised ofa doped polycrystalline III-V semiconductor material.
 14. Thesemiconductor device of claim 11, further comprising a doped singlecrystalline III-V semiconductor material that is present atop the baseregion.
 15. The semiconductor device of claim 10, wherein the substrateis comprised of a III-V semiconductor material.
 16. The semiconductordevice of claim 10, wherein the substrate semiconductor material isindium phosphide (InP).
 17. The semiconductor device of claim 10,wherein the base region is comprised of indium gallium arsenide(InGaAs).
 18. The semiconductor device of claim 10, wherein the emitterregion and the collector region are a type III-V semiconductor includingaluminum to increase a band gap of a second III-V semiconductor materialcomprising the emitter and collector regions to be greater than a firstIII-V semiconductor material comprising the base region.
 19. Thesemiconductor device of claim 10, wherein a position of the facetsprovide that an upper surface of the air gap fill is in direct contactwith the base surface for the entirety of each of said base region andsaid emitter and collector regions.